Jaro winkler

strings/jaro_winkler.py

@@ -2,7 +2,7 @@
 import math
 
 
-def jaro_winkler(first_string: str, second_string: str) -> float:
+def jaro_winkler(str1: str, str2: str) -> float:
     """
     Jaro–Winkler distance is a string metric measuring an edit distance between two sequences.
     Output value is between 0.0 and 1.0.
@@ -11,7 +11,7 @@ def jaro_winkler(first_string: str, second_string: str) -> float:
     0.9611111111111111
 
     >>> jaro_winkler("CRATE", "TRACE")
-    0.6222222222222222
+    0.7333333333333334
 
     >>> jaro_winkler("test", "dbdbdbdb")
     0.0
@@ -20,36 +20,50 @@ def jaro_winkler(first_string: str, second_string: str) -> float:
     1.0
 
     >>> jaro_winkler("hello world", "HeLLo W0rlD")
-    0.5303030303030303
+    0.6363636363636364
 
     >>> jaro_winkler("test", "")
     0.0
+
+    >>> jaro_winkler("hello", "world")
+    0.4666666666666666
+
+    >>> jaro_winkler("hell**o", "*world")
+    0.4365079365079365
     """
-    max_distance = math.floor(max(len(first_string), len(second_string)) / 2) - 1
+
+    def get_matched_characters(_str1, _str2):
+        matched = []
+        limit = math.floor(min(len(_str1), len(_str2)) / 2)
+        for i, l in enumerate(_str1):
+            left, right = int(max(0, i - limit)), int(min(i + limit + 1, len(_str2)))
+            if l in _str2[left:right]:
+                matched.append(l)
+                _str2 = _str2[0:_str2.index(l)] + " " + _str2[_str2.index(l) + 1:]
+
+        return ''.join(matched)
 
     # matching characters
-    match_count = 0
-    for i, c1 in enumerate(first_string):
-        for j, c2 in enumerate(second_string):
-            if c1 == c2 and abs(i - j) < max_distance:
-                match_count += 1
+    matching_1 = get_matched_characters(str1, str2)
+    matching_2 = get_matched_characters(str2, str1)
+    match_count = len(matching_1)
 
     # transposition
-    not_match = len(
-        [(c1, c2) for c1, c2 in zip(first_string, second_string) if c1 != c2]
-    )
+    transpositions = math.floor(len(
+        [(c1, c2) for c1, c2 in zip(matching_1, matching_2) if c1 != c2]
+    )) / 2
 
     if not match_count:
         jaro = 0.0
     else:
         jaro = 1 / 3 * (
-            match_count / len(first_string)
-            + match_count / len(second_string)
-            + (match_count - not_match / 2) / match_count)
+            match_count / len(str1)
+            + match_count / len(str2)
+            + (match_count - transpositions) / match_count)
 
     # common prefix up to 4 characters
     prefix_len = 0
-    for c1, c2 in zip(first_string[:4], second_string[:4]):
+    for c1, c2 in zip(str1[:4], str2[:4]):
         if c1 == c2:
             prefix_len += 1
         else: